Theabrownin fermented milk and preparation method thereof

Abstract

The invention discloses theabrownin fermented milk and a preparation method thereof, and belongs to the field of dairy product processing. The method comprises the following steps: pouring the milk and the cane sugar into a pre-disinfected container, preheating to 50-55 DEG C, adding the theabrownin, and stirring until the theabrownin is completely dissolved; homogenizing the obtained product, sterilizing, cooling to 42 DEG C, adding lactobacillus bulgaricus and streptococcus thermophilus, and stirring to completely ferment; and culturing the inoculated milk sample at 42 DEG C for 4 hours to obtain the theabrownin fermented milk. The main functional component theabrownin in the functional fermented milk product disclosed by the invention has remarkable effects of reducing blood sugar, blood fat, blood pressure, uric acid and the like, and the theabrownin has excellent acid-heat stability and has a beneficial effect of improving the comprehensive metabolic balance of a human body.

Description

Technical Field

[0001] The invention belongs to the field of dairy product processing, and particularly relates to theabrownin fermented milk and a preparation method thereof. Background Art

[0002] Fermented milk is widely popular for its unique flavor, excellent nutrition and health benefits. It is a fermented dairy product, mainly made from milk, and is often fermented using bacteria such as thermophilic Streptococcus and bulgaricus. Fermented milk is rich in vitamins and minerals, as well as protein, polysaccharides and fat. With the development of the food industry, consumers' demand for fermented milk is becoming increasingly diversified, and they pay more and more attention to the taste and functional characteristics of fermented milk. The quality requirements for fermented milk will also gradually increase. Therefore, it is particularly important to develop flavored fermented milk rich in functional factors. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects in the prior art and provide a theabrownin fermented milk and a preparation method thereof. The fermented milk provided by the present invention is a new type of health-care fermented milk with a unique flavor of tea, which has both the nutritional value of fermented milk and the health-care function of theabrownin.

[0004] The specific technical solutions adopted by the present invention are as follows:

[0005] In a first aspect, the present invention provides a method for preparing theabrownin fermented milk, which is as follows:

[0006] Pour milk and sucrose into a pre-sterilized container, preheat to 50°C-55°C, cool to 42°C and add theabrownin, and stir until theabrownin is completely dissolved; homogenize the resulting product, sterilize and cool to 42°C, add Lactobacillus bulgaricus and Streptococcus thermophilus, and stir to fully ferment; culture the inoculated milk sample at 42°C for 4 hours to obtain theabrownin fermented milk.

[0007] Preferably, the added amount of sucrose is 6% of the mass of milk.

[0008] Preferably, the added amount of theabrownin is 0.1 g / dL to 0.3 g / dL.

[0009] Preferably, the sterilization operation is performed at 120° C. for 5-10 seconds.

[0010] Preferably, the concentrations of Lactobacillus bulgaricus and Streptococcus thermophilus are both 1 g / dL.

[0011] Preferably, the mixing volume ratio of Lactobacillus bulgaricus and Streptococcus thermophilus is 1:1.

[0012] Preferably, the holding time after preheating is 10 minutes.

[0013] Preferably, the stirring fermentation time is 15 minutes.

[0014] Preferably, the storage temperature of the theabrownin fermented milk is 4°C.

[0015] In a second aspect, the present invention provides a theabrownin fermented milk obtained by any preparation method described in the first aspect.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The main functional ingredient theabrownin in the functional fermented milk product of the present invention has significant effects on lowering blood sugar, blood lipids, blood pressure, uric acid, etc. Theabrownin has excellent acid and heat stability and has a beneficial effect on improving the comprehensive metabolic balance of the human body. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : These are the changes in (A) pH value, (B) acidity, (C) water retention capacity, and (D) lactic acid bacteria count of theabrownin fermented milk during storage in the examples.

[0019] Figure 2 The microstructural characteristics of theabrownin fermented milk under a 5.0kX scanning electron microscope. DETAILED DESCRIPTION

[0020] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0021] The present invention provides a method for preparing theabrownin fermented milk, and the preparation method is specifically as follows:

[0022] S1: Pour milk into a pre-sterilized container, add sucrose, preheat to 50℃-55℃, then cool to 42℃ and add theabrownin, stirring until theabrownin is completely dissolved.

[0023] As a preferred embodiment of the present invention, the added amount of sucrose is 6% of the mass of milk.

[0024] As a preferred embodiment of the present invention, during the heat treatment process, the theabrownin sample (0.1 g / dL to 0.3 g / dL) is gradually added to the milk by mechanical stirring until it is completely dissolved.

[0025] As a preferred embodiment of the present invention, the holding time after preheating is 10 minutes.

[0026] S2: The obtained product is homogenized, sterilized, cooled to 42°C, and Lactobacillus bulgaricus and Streptococcus thermophilus are added, and stirred to fully ferment.

[0027] As a preferred embodiment of the present invention, the sterilization operation is sterilization at 120° C. for 5-10 seconds.

[0028] As a preferred embodiment of the present invention, the concentrations of Lactobacillus bulgaricus and Streptococcus thermophilus are both 1 g / dL, and the mixed volume ratio of Lactobacillus bulgaricus and Streptococcus thermophilus is 1:1.

[0029] As a preferred embodiment of the present invention, the stirring and fermentation time is 15 minutes.

[0030] S3: The inoculated milk sample is cultured at 42° C. for 4 hours to obtain theabrownin fermented milk.

[0031] As a preferred embodiment of the present invention, the storage temperature of theabrownin fermented milk is 4°C.

[0032] The present invention studies and evaluates the effect of theabrownin addition on fermented milk. The addition of different concentrations of theabrownin (0.1 g / dL to 0.3 g / dL) can improve the physical and chemical properties and antioxidant properties of fermented milk. During storage, the addition of theabrownin can reduce the pH value of fermented milk, increase water retention capacity, total phenol content and antioxidant activity.

[0033] The preparation method and effects of the present invention will be specifically described below through examples.

[0034] Example

[0035] This embodiment prepares a theabrownin fermented milk, and the preparation method is as follows:

[0036] 300g of milk was poured into a pre-sterilized container, followed by the addition of 18g of sucrose, preheated to 50°C, then cooled to 42°C and theabrownin (0.1g / dL and 0.3g / dL) was added, and stirred until theabrownin was completely dissolved. The resulting product was homogenized, sterilized at 120°C for 5-10s, cooled to 42°C, and Lactobacillus bulgaricus (1g / dL) and Streptococcus thermophilus (1g / dL) were added in a 1:1 volume ratio, and stirred for 15min to fully ferment. The inoculated milk sample was cultured at 42°C for 4h to obtain theabrownin fermented milk, which was stored at 4°C for 1, 7, 14 and 21 days until analysis.

[0037] The following experimental analysis was conducted on the theabrownin fermented milk prepared in this example:

[0038] 1. Determination of pH value and acidity:

[0039] The theabrownin fermented milk samples were directly measured with a pH meter, and the measurement time was synchronized with the titration acidity. The titration acidity determination method refers to GB 5413.34-2010. Take 10g of sample and place it in a 250mL conical flask, add 20mL of purified water and mix well, then add 0.5mL of phenolphthalein indicator with a concentration of 5g / L, and then titrate with 0.100mol / L sodium hydroxide standard solution. If the solution is dripped to a slightly reddish color and does not fade for 30s, multiply the milliliters of the consumed sodium hydroxide standard solution by 10 to obtain the titration acidity (°T). From each group of samples, take 1 bottle of sample for titration acidity determination, store for 1, 7, 14 and 21 days for determination, and measure 3 times in parallel each time, and take the average value.

[0040] The results of changes in pH and titrated acidity showed that the pH of the theabrownin fermented milk sample was lower than that of the control group (i.e., the preparation method was the same as that in the example, but theabrownin was not added), and the titrated acidity was higher than that of the control group. During storage, the pH of the theabrownin fermented milk decreased ( Figure 1 A). As the concentration of theabrownin increased, the pH value of theabrownin fermented milk samples showed a downward trend, while the titrated acidity showed an upward trend. However, the titrated acidity of theabrownin fermented milk was higher than that of the control group during the entire storage period ( Figure 1 B).

[0041] 2. Determination of water holding capacity:

[0042] The water holding capacity of theabrownin fermented milk was measured. 10g of fermented milk sample was added to a 50mL centrifuge tube and centrifuged at 4000rpm for 10min at 4°C. The sediment was placed upside down for 10min and the weight of the sediment was weighed. The water holding capacity was calculated as follows:

[0043] Water holding capacity (%) = sediment mass (g) / initial sample mass (g) × 100%

[0044] The results showed that the water holding capacity of fermented milk samples with 0.1g / dL and 0.3g / dL theabrownin added increased. The water holding capacity of the fermented milk samples was stable from the first to the seventh day. However, after the 14th day, structural decomposition occurred, which was manifested by a gradual decrease in water holding capacity until the 21st day ( Figure 1 C).

[0045] 3. Detection of live lactic acid bacteria

[0046] The theabrownin fermented milk samples were tested for the number of viable lactic acid bacteria at 1, 7, 14 and 21 days of storage. 1g of fermented milk was diluted with 9mL of sterile peptone water (0.1g / 100mL), and then diluted continuously with peptone water (1:10). 1mL of each dilution was applied to M17 (Thermophilic Streptococcus) and MRS (Bulgarian Streptococcus). Incubate at 37℃ for 3 days (M17, Thermophilic Streptococcus), incubate under anaerobic conditions for 2 days (MRS, Bulgarian Streptococcus), and incubate at 37℃ for 5 days (PDA, yeast and mold). The logarithm of the number of colony forming units per gram of fermented milk (log CFU / g) was obtained by three repeated analyses.

[0047] Microbiological analysis results Figure 1 As shown in Figure D, it can be seen that during the storage of fermented milk, the addition of theabrownin has an impact on the viability of Lactobacillus bulgaricus and Streptococcus thermophilus. In general, as the concentration of theabrownin increases, the number of viable bacteria also increases. It is speculated that theabrownin may contain beneficial ingredients that promote the proliferation of lactic acid bacteria.

[0048] 4. Detection of microstructural characteristics

[0049] The microstructural characteristics of fermented milk samples were examined using scanning electron microscopy. The fermented milk samples were examined under a 7kV high vacuum scanning electron microscope, and micrographs of the fermented milk samples were recorded at a magnification of 2kX. At least 8 areas of different samples were examined, and the image with the best contrast was selected to represent the microstructure of the sample. The results are shown in Figure 2. Figure 2 As shown, Figure 2 A is the microscopic structure of fermented milk without theabrownin added. Figure 2 B is the microscopic structure of fermented milk with 0.1g / dL theabrownin added. Figure 2 C is a microstructure diagram of fermented milk with 0.3 g / dL theabrownin added. As can be seen from the figure, the control sample has a discontinuous branching network with obvious gaps. However, as the concentration of theabrownin increases, the three-dimensional network structure of the fermented milk becomes more compact, showing a uniform microstructure with few or no pores. The addition of theabrownin makes the microstructure of the fermented milk finer and denser.

[0050] 5. Evaluation of Antioxidant (ABTS) Activity

[0051] The fermented milk sample was centrifuged at 4°C, 8000rpm for 10min, 10g of supernatant was transferred to a 50mL centrifuge tube, 15mL of acidified methanol containing 0.05mL of concentrated hydrochloric acid was added, mixed evenly immediately, kept at -20°C for 1h to completely precipitate the protein, and centrifuged at 4°C, 5000rpm for 10min. After centrifugation, the supernatant was taken to determine the total phenol content (TPC) of theabrownin fermented milk and evaluate the scavenging ability of 2,2'-azobis-3-ethylbenzothiazoline-6-sulfonic acid free radical (ABTS). Briefly, 50μL of fermented milk supernatant was mixed with 200μL of ABTS working solution on a 96-well microplate. After incubation for 30 minutes, the absorbance was measured at 405nm relative to the control.

[0052] Theabrownin fermented milk can significantly increase the total phenol content and antioxidant activity (Table 1). On the first day of storage, the total phenol content of fermented milk containing 0.1g / dLTB and 0.3g / dL theabrownin was 26.67% and 54.29% higher than that of the control group, respectively. ABTS activity increased with the increase of theabrownin content, among which the ABTS activity of fermented milk fortified with 0.3g / dL theabrownin was the highest.

[0053] Table 1. Changes in total phenol content and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid free radical scavenging ability during storage of theabrownin fermented milk

[0054]

[0055] *The results are expressed as mean ± standard deviation (n = 3). The same letters have no significant difference by Duncan test (p ≤ 0.05).

[0056] The present invention successfully prepares a novel functional fermented milk with a unique tea flavor by adding theabrownin to fermented milk, which not only greatly improves the nutritional value of the fermented milk, but also brings in the unique flavor and taste of tea, greatly satisfying people's pursuit of the functional flavor and taste of fermented milk. Theabrownin has health care effects such as anti-oxidation, lowering blood lipids, preventing and treating cardiovascular and cerebrovascular diseases, antibacterial and antiviral, anti-inflammatory, and anti-tumor. Moreover, theabrownin is helpful to prolong the storage period of fermented milk, and its antioxidant capacity gives the fermented milk a better health care effect. Its flavor is well received and has a good market prospect.

[0057] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for preparing theabrownin fermented milk, characterized in that: The details are as follows: Pour milk and sucrose into a pre-sterilized container, preheat to 50°C-55°C, cool to 42°C and add theabrownin, and stir until theabrownin is completely dissolved; homogenize the resulting product, sterilize and cool to 42°C, add Lactobacillus bulgaricus and Streptococcus thermophilus, and stir to fully ferment; culture the inoculated milk sample at 42°C for 4 hours to obtain theabrownin fermented milk.

2. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The added amount of the sucrose is 6% of the mass of the milk.

3. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The added amount of theabrownin is 0.1 g / dL to 0.3 g / dL.

4. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The sterilization operation is sterilized at 120° C. for 5-10 seconds.

5. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The concentrations of Lactobacillus bulgaricus and Streptococcus thermophilus were both 1 g / dL.

6. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The mixing volume ratio of the Lactobacillus bulgaricus and Streptococcus thermophilus is 1:

1.

7. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The holding time after preheating is 10 minutes.

8. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The stirring and fermenting time is 15 minutes.

9. The method for preparing theabrownin fermented milk according to claim 1, characterized in that: The storage temperature of the theabrownin fermented milk is 4°C.

10. Theabrownin fermented milk obtained by the preparation method according to any one of claims 1 to 9.

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